Ultragenyx Pharmaceutical Inc. announced recently that it would exercise its option to buy 600,000 shares of Arcturus Therapeutics Holdings Inc.'s common stock at $16 per share.

San Diego-based Arcturus is a messenger RNA medicines company that is working on a vaccine for COVID-19.

Ultragenyx is a biopharmaceutical company focused on the development and commercialization of novel products for serious rare and ultra-rare genetic diseases, according to the company

“The new investment from Ultragenyx is a testament to the strength of our long-term collaboration in developing nucleic acid therapies,” said Andrew Sassine, chief financial officer of Arcturus. “The additional funding will support our clinical programs, including our efforts to move our COVID-19 vaccine candidate into clinical testing this summer.”